Restriction plug element and method

ABSTRACT

A restriction plug element and method for positioning plugs to isolate fracture zones in a horizontal, vertical, or deviated wellbore is disclosed. The restriction plug element includes a partial hollow passage with an interior end. The partial passage enables the plug element to seat in a restriction sleeve member during treatment and subsequently degrade to form a complete hollow passage. The complete flow channel dissolves or degrades not only the outside but also the inside of the wall of the restriction plug element. Initially the flow is restricted by the closed end in the partial hollow passage and over time the flow channel opens up by degradation and allows fluid to pass through in either direction. During back flow in the well new fluid is circulated into the well and the restriction plug element continues to degrade.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.14/721,784, filed May 26, 2015, which claims the benefit of U.S.Provisional No. 62/081,399, filed Nov. 18, 2014, which is also acontinuation-in-part of U.S. application Ser. No. 14/459,042, filed Aug.13, 2014, now U.S. Pat. No. 9,062,543, the disclosures of which arefully incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to oil and gas extraction.Specifically, the invention attempts to isolate fracture zones throughselectively positioning restriction elements within a wellbore casing.

PRIOR ART AND BACKGROUND OF THE INVENTION

Prior Art Background

The process of extracting oil and gas typically consists of operationsthat include preparation, drilling, completion, production andabandonment.

Preparing a drilling site involves ensuring that it can be properlyaccessed and that the area where the rig and other equipment will beplaced has been properly graded. Drilling pads and roads must be builtand maintained which includes the spreading of stone on an impermeableliner to prevent impacts from any spills but also to allow any rain todrain properly.

In the drilling of oil and gas wells, a wellbore is formed using a drillbit that is urged downwardly at a lower end of a drill string. Afterdrilling the wellbore is lined with a string of casing. An annular areais thus formed between the string of casing and the wellbore. Acementing operation is then conducted in order to fill the annular areawith cement. The combination of cement and casing strengthens thewellbore and facilitates the isolation of certain areas of the formationbehind the casing for the production of hydrocarbons.

The first step in completing a well is to create a connection betweenthe final casing and the rock which is holding the oil and gas. Thereare various operations in which it may become necessary to isolateparticular zones within the well. This is typically accomplished bytemporarily plugging off the well casing at a given point or points witha plug.

A special tool, called a perforating gun, is lowered to the rock layer.This perforating gun is then fired, creating holes through the casingand the cement and into the targeted rock. These perforating holesconnect the rock holding the oil and gas and the well bore.

Since these perforations are only a few inches long and are performedmore than a mile underground, no activity is detectable on the surface.The perforation gun is then removed before the next step, hydraulicfracturing. Stimulation fluid, which is a mixture of over 90% water andsand, plus a few chemical additives, is pumped under controlledconditions into deep, underground reservoir formations. The chemicalsare used for lubrication and to keep bacteria from forming and to carrythe sand. These chemicals are typically non-hazardous and range inconcentrations from 0.1% to 0.5% by volume and are needed to helpimprove the performance and efficiency of the hydraulic fracturing. Thisstimulation fluid is pumped at high pressure out through theperforations made by the perforating gun. This process creates fracturesin the shale rock which contains the oil and natural gas.

In many instances a single wellbore may traverse multiple hydrocarbonformations that are otherwise isolated from one another within theEarth. It is also frequently desired to treat such hydrocarbon bearingformations with pressurized treatment fluids prior to producing fromthose formations. In order to ensure that a proper treatment isperformed on a desired formation, that formation is typically isolatedduring treatment from other formations traversed by the wellbore. Toachieve sequential treatment of multiple formations, the casing adjacentto the toe of a horizontal, vertical, or deviated wellbore is firstperforated while the other portions of the casing are left unperforated.The perforated zone is then treated by pumping fluid under pressure intothat zone through perforations. Following treatment a plug is placedadjacent to the perforated zone. The process is repeated until all thezones are perforated. The plugs are particularly useful in accomplishingoperations such as isolating perforations in one portion of a well fromperforations in another portion or for isolating the bottom of a wellfrom a wellhead. The purpose of the plug is to isolate some portion ofthe well from another portion of the well.

Subsequently, production of hydrocarbons from these zones requires thatthe sequentially set plugs be removed from the well. In order toreestablish flow past the existing plugs an operator must remove and/ordestroy the plugs by milling, drilling, or dissolving the plugs.

Restriction plug elements such as balls/plugs with large aspect ratioapproaching 1 and seated in a large inner diameter restriction sleevemember do not degrade in wellbore fluids. The plug elements change shapefrom a circular to flying saucer shape because water is restricted onthe edges and a sand pack that holds the ball on the seat prevents theplug element from interacting with the water and wellbore fluids.Therefore there is a need to add a mechanism to provide more surfacearea in the restriction plug element to provide contact with therestriction plug element after seating in a restriction sleeve member.

Prior Art System Overview (0100)

As generally seen in the system diagram of FIG. 1 (0100), prior artsystems associated with oil and gas extraction may include a wellborecasing (0120) laterally drilled into a wellbore. A plurality of fracplugs (0110, 0111, 0112, 0113) may be set to isolate multiple hydraulicfracturing zones (0101, 0102, 0103). Each frac plug is positioned toisolate a hydraulic fracturing zone from the rest of the unperforatedzones. The positions of frac plugs may be defined by preset sleeves inthe wellbore casing. For example, frac plug (0111) is positioned suchthat hydraulic fracturing zone (0101) is isolated from downstream(injection or toe end) hydraulic fracturing zones (0102, 0103).Subsequently, the hydraulic fracturing zone (0101) is perforated using aperforation gun and fractured. Preset plug/sleeve positions in thecasing, precludes change of fracture zone locations after a wellborecasing has been installed. Therefore, there is a need to position a plugat a desired location after a wellbore casing has been installed withoutdepending on a predefined sleeve location integral to the wellborecasing to position the plug.

Furthermore, after well completion, sleeves used to set frac plugs mayhave a smaller inner diameter constricting fluid flow when wellproduction is initiated. Therefore, there is a need for relatively largeinner diameter sleeves after well completion that allow for unrestrictedwell production fluid flow.

Additionally, frac plugs can be inadvertently set at undesired locationsin the wellbore casing creating unwanted constrictions. Theconstrictions may latch wellbore tools that are run for futureoperations and cause unwanted removal process. Therefore, there is aneed to prevent premature set conditions caused by conventional fracplugs.

Prior Art Method Overview (0200)

As generally seen in the method of FIG. 2 (0200), prior art associatedwith oil and gas extraction includes site preparation and installationof a wellbore casing (0120) (0201). Preset sleeves may be installed asan integral part of the wellbore casing (0120) to position frac plugsfor isolation. After setting a frac plug and isolating a hydraulicfracturing zone in step (0202), a perforating gun is positioned in theisolated zone in step (0203). Subsequently, the perforating gundetonates and perforates the wellbore casing and the cement into thehydrocarbon formation. The perforating gun is next moved to an adjacentposition for further perforation until the hydraulic fracturing zone iscompletely perforated. In step (0204), hydraulic fracturing fluid ispumped into the perforations at high pressures. The steps comprisingsetting up a plug (0202), isolating a hydraulic fracturing zone,perforating the hydraulic fracturing zone (0203) and pumping hydraulicfracturing fluids into the perforations (0204), are repeated until allhydraulic fracturing zones in the wellbore casing are processed. In step(0205), if all hydraulic fracturing zones are processed, the plugs aremilled out with a milling tool and the resulting debris is pumped out orremoved from the wellbore casing (0206). In step (0207) hydrocarbons areproduced by pumping out from the hydraulic fracturing stages.

The step (0206) requires that removal/milling equipment be run into thewell on a conveyance string which may typically be wire line, coiledtubing or jointed pipe. The process of perforating and plug settingsteps represent separate “trip” into and out of the wellbore with therequired equipment. Each trip is time consuming and expensive. Inaddition, the process of drilling and milling the plugs creates debristhat needs to be removed in another operation. Therefore, there is aneed for isolating multiple hydraulic fracturing zones without the needfor a milling operation. Furthermore, there is a need for positioningrestrictive plug elements that could be removed in a feasible, economic,and timely manner before producing gas.

Deficiencies in the Prior Art

The prior art as detailed above suffers from the following deficiencies:

-   -   Prior art systems do not provide for positioning a ball seat at        a desired location after a wellbore casing has been installed,        without depending on a predefined sleeve location integral to        the wellbore casing to position the plug.    -   Prior art systems do not provide for isolating multiple        hydraulic fracturing zones without the need for a milling        operation.    -   Prior art systems do not provide for positioning restrictive        elements that could be removed in a feasible, economic, and        timely manner.    -   Prior art systems do not provide for setting larger inner        diameter sleeves to allow unrestricted well production fluid        flow.    -   Prior art systems cause undesired premature preset conditions        preventing further wellbore operations.

While some of the prior art may teach some solutions to several of theseproblems, the core issue of isolating hydraulic fracturing zones withoutthe need for a milling operation has not been addressed by prior art.

OBJECTIVES OF THE INVENTION

Accordingly, the objectives of the present invention are (among others)to circumvent the deficiencies in the prior art and affect the followingobjectives:

-   -   Provide for positioning a ball seat at a desired location after        a wellbore casing has been installed, without depending on a        predefined sleeve location integral to the wellbore casing to        position the plug.    -   Provide for isolating multiple hydraulic fracturing zones        without the need for a milling operation.    -   Provide for positioning restrictive elements that could be        removed in a feasible, economic, and timely manner.    -   Provide for setting larger inner diameter sleeves to allow        unrestricted well production fluid flow.    -   Provide for eliminating undesired premature preset conditions        that prevent further wellbore operations.

While these objectives should not be understood to limit the teachingsof the present invention, in general these objectives are achieved inpart or in whole by the disclosed invention that is discussed in thefollowing sections. One skilled in the art will no doubt be able toselect aspects of the present invention as disclosed to affect anycombination of the objectives described above.

BRIEF SUMMARY OF THE INVENTION System Overview

The present invention in various embodiments addresses one or more ofthe above objectives in the following manner. The present inventionprovides a system to isolate fracture zones in a horizontal, vertical,or deviated wellbore without the need for a milling operation. Thesystem includes a restriction plug element for use in a wellbore casingcomprising a degradable material. The restriction plug elementconfigured with a partial hollow passage extending from at least oneinterior end configured to block fluid communication from upstream todownstream during fluid treatment. The partial hollow passage degradesand forms a complete hollow passage to enable the fluid communicationsubsequent to the fluid treatment.

Method Overview

The present invention system may be utilized in the context of anoverall gas extraction method, wherein the restriction plug elementdescribed previously is controlled by a method having the followingsteps:

-   -   (1) deploying the restriction plug element into the wellbore        casing and blocking fluid communication;    -   (2) orienting the restriction plug element with the interior end        to seat in a restriction sleeve member and isolating a stage;    -   (3) treating the isolated stage with fracturing fluids;    -   (4) degrading from the interior end in the partial hollow        passage through contact with wellbore fluids;    -   (5) creating a complete hollow passage from the partial hollow        passage; and    -   (6) unblocking the fluid communication.

Integration of this and other preferred exemplary embodiment methods inconjunction with a variety of preferred exemplary embodiment systemsdescribed herein in anticipation by the overall scope of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the advantages provided by the invention,reference should be made to the following detailed description togetherwith the accompanying drawings wherein:

FIG. 1 illustrates a system block overview diagram describing how priorart systems use plugs to isolate hydraulic fracturing zones.

FIG. 2 illustrates a flowchart describing how prior art systems extractgas from hydrocarbon formations.

FIG. 3 illustrates an exemplary system side view of a sphericalrestriction plug element/restriction sleeve member overview depicting apresently preferred embodiment of the present invention.

FIG. 3a illustrates an exemplary system side view of a sphericalrestriction plug element/restriction sleeve member overview depicting apresently preferred embodiment of the present invention.

FIG. 4 illustrates a side perspective view of a spherical restrictionplug element/restriction sleeve member depicting a preferred exemplarysystem embodiment.

FIG. 5 illustrates an exemplary wellbore system overview depictingmultiple stages of a preferred embodiment of the present invention.

FIG. 6 illustrates a detailed flowchart of a preferred exemplarywellbore plug isolation method used in some preferred exemplaryinvention embodiments.

FIG. 7 illustrates a side view of a cylindrical restriction plug elementseated in a restriction sleeve member depicting a preferred exemplarysystem embodiment.

FIG. 8 illustrates a side perspective view of a cylindrical restrictionplug element seated in a restriction sleeve member depicting a preferredexemplary system embodiment.

FIG. 9 illustrates a side view of a dart restriction plug element seatedin a restriction sleeve member depicting a preferred exemplary systemembodiment.

FIG. 10 illustrates a side perspective view of a dart restriction plugelement seated in a restriction sleeve member depicting a preferredexemplary system embodiment.

FIG. 10a illustrates a side perspective view of a dart restriction plugelement depicting a preferred exemplary system embodiment.

FIG. 10b illustrates another perspective view of a dart restriction plugelement depicting a preferred exemplary system embodiment.

FIG. 11 illustrates a side view of a restriction sleeve member sealedwith an elastomeric element depicting a preferred exemplary systemembodiment.

FIG. 12 illustrates a side perspective view of a restriction sleevemember sealed with gripping/sealing element depicting a preferredexemplary system embodiment.

FIG. 13 illustrates side view of an inner profile of a restrictionsleeve member sealed against an inner surface of a wellbore casingdepicting a preferred exemplary system embodiment.

FIG. 14 illustrates a detailed cross section view of a wellbore settingtool creating a seal according to a preferred exemplary systemembodiment.

FIG. 15 illustrates a wellbore setting tool creating inner and outerprofiles in the restriction sleeve member depicting a preferredexemplary system embodiment.

FIG. 16 illustrates a detailed cross section view of a wellbore settingtool creating inner profiles in the restriction sleeve member depictinga preferred exemplary system embodiment.

FIG. 17 illustrates a detailed cross section view of a wellbore settingtool creating inner profiles and outer profiles in the restrictionsleeve member depicting a preferred exemplary system embodiment.

FIG. 18 illustrates a cross section view of a wellbore setting toolsetting a restriction sleeve member depicting a preferred exemplarysystem embodiment.

FIG. 19 illustrates a detailed cross section view of a wellbore settingtool setting a restriction sleeve member depicting a preferred exemplarysystem embodiment.

FIG. 20 illustrates a detailed side section view of a wellbore settingtool setting a restriction sleeve member depicting a preferred exemplarysystem embodiment.

FIG. 21 illustrates a detailed perspective view of a wellbore settingtool setting a restriction sleeve member depicting a preferred exemplarysystem embodiment.

FIG. 22 illustrates another detailed perspective view of a wellboresetting tool setting a restriction sleeve member depicting a preferredexemplary system embodiment.

FIG. 23 illustrates a cross section view of a wellbore setting toolsetting a restriction sleeve member and removing the tool depicting apreferred exemplary system embodiment.

FIG. 24 illustrates a detailed cross section view of wellbore settingtool setting a restriction sleeve member depicting a preferred exemplarysystem embodiment.

FIG. 25 illustrates a cross section view of wellbore setting toolremoved from wellbore casing depicting a preferred exemplary systemembodiment.

FIG. 26 illustrates a cross section view of a spherical restriction plugelement deployed and seated into a restriction sleeve member depicting apreferred exemplary system embodiment.

FIG. 27 illustrates a detailed cross section view of a sphericalrestriction plug element deployed into a restriction sleeve memberdepicting a preferred exemplary system embodiment.

FIG. 28 illustrates a detailed cross section view of a sphericalrestriction plug element seated in a restriction sleeve member depictinga preferred exemplary system embodiment.

FIG. 29 illustrates a cross section view of wellbore setting toolsetting a restriction sleeve member and seating a second restrictionplug element depicting a preferred exemplary system embodiment.

FIG. 30 illustrates a detailed cross section view of wellbore settingtool setting a second restriction sleeve member depicting a preferredexemplary system embodiment.

FIG. 31 illustrates a detailed cross section view of a sphericalrestriction plug element seated in a second restriction sleeve memberdepicting a preferred exemplary system embodiment.

FIG. 32 illustrates a cross section view of a restriction sleeve memberwith flow channels according to a preferred exemplary system embodiment.

FIG. 33 illustrates a detailed cross section view of a restrictionsleeve member with flow channels according to a preferred exemplarysystem embodiment.

FIG. 34 illustrates a perspective view of a restriction sleeve memberwith flow channels according to a preferred exemplary system embodiment.

FIG. 35 illustrates a cross section view of a double set restrictionsleeve member according to a preferred exemplary system embodiment.

FIG. 36 illustrates a detailed cross section view of a double setrestriction sleeve member according to a preferred exemplary systemembodiment.

FIG. 37 illustrates a perspective view of a double set restrictionsleeve member according to a preferred exemplary system embodiment.

FIG. 38 illustrates a cross section view of a WST setting restrictionsleeve member at single, double and triple locations according to apreferred exemplary system embodiment.

FIG. 39 illustrates a cross section view of a WST with triple setrestriction sleeve member according to a preferred exemplary systemembodiment.

FIG. 40 illustrates a detailed cross section view of a triple setrestriction sleeve member according to a preferred exemplary systemembodiment.

FIG. 41 illustrates a detailed perspective view of a triple setrestriction sleeve member according to a preferred exemplary systemembodiment.

FIG. 42 illustrates cross section and perspective views of a restrictionplug element with a partial hollow passage according to a preferredexemplary system embodiment.

FIG. 43 illustrates cross section and perspective views of a restrictionplug element with a plurality of partial hollow passages according to apreferred exemplary system embodiment.

FIG. 44 illustrates perspective views of a restriction plug elementtransforming a partial hollow passage into a complete hollow passageaccording to a preferred exemplary system embodiment.

FIG. 45 illustrates cross section and perspective views of a restrictionplug element with a partial hollow passage that extends to a surface onboth ends according to a preferred exemplary system embodiment.

FIG. 46 illustrates an exemplary flowchart embodiment of a restrictionplug element degradation method.

FIG. 47 illustrates a mass vs. time chart for a solid ball and anexemplary restriction plug element with a partial hollow passageaccording to a preferred exemplary embodiment.

FIG. 48 illustrates a diameter vs. time chart for a solid ball and anexemplary restriction plug element with a partial hollow passageaccording to a preferred exemplary embodiment.

DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetailed preferred embodiment of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiment illustrated.

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiment, wherein these innovative teachings are advantageouslyapplied to the particular problems of a wellbore plug isolation systemand method. However, it should be understood that this embodiment isonly one example of the many advantageous uses of the innovativeteachings herein. In general, statements made in the specification ofthe present application do not necessarily limit any of the variousclaimed inventions. Moreover, some statements may apply to someinventive features but not to others.

GLOSSARY OF TERMS

-   -   RSM: Restriction Sleeve Member, a cylindrical member positioned        at a selected wellbore location.    -   RPE: Restriction Plug Element, an element configured to isolate        and block fluid communication.    -   CSS: Conforming Seating Surface, a seat formed within RSM.    -   ICD: Inner Casing Diameter, inner diameter of a wellbore casing.    -   ICS: Inner Casing Surface, inner surface of a wellbore casing.    -   ISD: Inner Sleeve Diameter, inner diameter of a RSM.    -   ISS: Inner Sleeve Surface, inner surface of a RSM.    -   WST: Wellbore Setting Tool, a tool that functions to set and        seal RSMs.    -   GSA: Gun String Assembly, a cascaded string of perforating guns        coupled to each other.

Preferred Embodiment System Block Diagram (0300, 0400)

The present invention may be seen in more detail as generallyillustrated in FIG. 3 (0300) and FIG. 3a (0320), wherein a wellborecasing (0304) is installed inside a hydrocarbon formation (0302) andheld in place by wellbore cement (0301). The wellbore casing (0304) mayhave an inner casing surface (ICS) associated with an inner casingdiameter (ICD) (0308). For example, ICD (0308) may range from 2¾ inch to12 inches. A restriction sleeve member (RSM) (0303) that fits inside ofthe wellbore casing is disposed therein by a wellbore setting tool (WST)to seal against the inside surface of the wellbore casing. The seal maybe leaky or tight depending on the setting of RSM (0303). The RSM (0303)may be a hollow cylindrical member having an inner sleeve surface and anouter sleeve surface. The RSM (0303) may be concentric with the wellborecasing and coaxially fit within the ICS. In one preferred exemplaryembodiment, the seal prevents RSM (0303) from substantial axially orlongitudinally sliding along the inside surface of the wellbore casing.The RSM (0303) may be associated with an inner sleeve diameter (ISD)(0307) that is configured to fit within ICD (0308) of the wellborecasing (0304). In another preferred exemplary embodiment, ISD (0307) islarge enough to enable unrestricted fluid movement through inner sleevesurface (ISS) during production. The ratio of ISD (0307) to ICD (0308)may range from 0.5 to 0.99. For example, ICD may be 4.8 inches and ISDmay be 4.1 inches. In the foregoing example, the ratio of ISD (0307) andICD (0308) is 0.85. The diameter of ISD (0307) may further degradeduring production from wellbore fluids enabling fluid flow on almost theoriginal diameter of the well casing. In a further preferred exemplaryembodiment, RSM (0303) may be made from a material comprising ofaluminum, iron, steel, titanium, tungsten, copper, bronze, brass,plastic, composite, natural fiber, and carbide. The RSM (0303) may bemade of degradable material or a commercially available material.

In a preferred exemplary embodiment, the WST may set RSM (0303) to theICS in compression mode to form an inner profile on the RSM (0303). Theinner profile could form a tight or leaky seal preventing substantialaxial movement of the RSM (0303). In another preferred exemplaryembodiment, the WST may set RSM (0303) to the ICS in expansion modeproviding more contact surface for sealing RSM (0303) against ICS.Further details of setting RSM (0303) through compression and expansionmodes are further described below in FIG. 15.

In another preferred exemplary embodiment, the WST may set RSM (0303)using a gripping/sealing element disposed of therein with RSM (0303) togrip the outside surface of RSM (0303) to ICS. Further details ofsetting RSM (0303) through compression and expansion modes are describedbelow in FIG. 11 (1100).

In another preferred exemplary embodiment, the WST may set RSM (0303) atany desired location within wellbore casing (0304). The desired locationmay be selected based on information such as the preferred hydrocarbonformation area, fraction stage, and wellbore conditions. The desiredlocation may be chosen to create uneven hydraulic fracturing stages. Forexample, a shorter hydraulic fracturing stage may comprise a singleperforating position so that the RSM locations are selected close toeach other to accommodate the perforating position. Similarly, a longerhydraulic fracturing stage may comprise multiple perforating positionsso that the RSM locations are selected as far to each other toaccommodate the multiple perforating positions. Shorter and longerhydraulic fracturing positions may be determined based on the specificinformation of hydrocarbon formation (0302). A mudlog analyzes the mudduring drilling operations for hydrocarbon information at locations inthe wellbore. Prevailing mudlog conditions may be monitored todynamically change the desired location of RSM (0303).

The WST may create a conforming seating surface (CSS) (0306) within RSM(0303). The WST may form a beveled edge on the production end (heel end)of the RSM (0303) by constricting the inner diameter region of RSM(0303) to create the CSS (0306). The inner surface of the CSS (0306)could be formed such that it seats and retains a restriction plugelement (RPE) (0305). The diameter of the RPE (0305) is chosen such thatit is less than the outer diameter and greater than the inner diameterof RSM (0303). The CSS (0306) and RPE (0305) may be complementary shapedsuch that RPE (0305) seats against CSS (0306). For example, RPE (0306)may be spherically shaped and the CSS (0306) may be beveled shaped toenable RPE (0305) to seat in CSS (0306) when a differential pressure isapplied. The RPE (0305) may pressure lock against CSS (0306) whendifferential pressure is applied i.e., when the pressure upstream(production or heel end) of the RSM (0303) location is greater than thepressure downstream (injection or toe end) of the RSM (0303). Thedifferential pressure established across the RSM (0303) locks RPE (0305)in place isolating downstream (injection or toe end) fluidcommunication. According to one preferred exemplary embodiment, RPE(0305) seated in CSS (0306) isolates a zone to enable hydraulicfracturing operations to be performed in the zone without affectingdownstream (injection or toe end) hydraulic fracturing stages. The RPE(0305) may also be configured in other shapes such as a plug, dart or acylinder. It should be noted that one skilled in the art wouldappreciate that any other shapes conforming to the seating surface maybe used for RPEs to achieve similar isolation affect as described above.

According to another preferred exemplary embodiment, RPE (0305) may seatdirectly in RSM (0303) without the need for a CSS (0306). In thiscontext, RPE (0305) may lock against the vertical edges of the RSM(0303) which may necessitate a larger diameter RPE (0305).

According to yet another preferred exemplary embodiment, RPE (0305) maydegrade over time in the well fluids eliminating the need to be removedbefore production. The RPE (0305) degradation may also be accelerated byacidic components of hydraulic fracturing fluids or wellbore fluids,thereby reducing the diameter of RPE (0305) enabling it to flow out(pump out) of the wellbore casing or flow back (pump back) to thesurface before production phase commences.

In another preferred exemplary embodiment, RPE (0305) may be made of ametallic material, non-metallic material, a carbide material, or anyother commercially available material.

Preferred Embodiment Multistage System Diagram (0500)

The present invention may be seen in more detail as generallyillustrated in FIG. 5 (0500), wherein a wellbore casing (0504) is shownafter hydraulic fracturing is performed in multiple stages (fractureintervals) according to a method described herewith below in FIG. 6(0600). A plurality of stages (0520, 0521, 0522, 0523) are created bysetting RSMs (0511, 0512, 0513) at desired positions followed byisolating each stage successively with restriction plug elements RPEs(0501, 0502, 0503). A RSM (0513) may be set by a WST followed bypositioning a perforating gun string assembly (GSA) in hydraulicfracturing zone (0522) and perforating the interval. Subsequently, RPE(0503) is deployed and the stage (0522) is hydraulically fractured. TheWST and the perforating GSA are removed for further operations.Thereafter, RSM (0512) is set and sealed by WST followed by aperforation operation. Another RPE (0502) is deployed to seat in RSM(0512) to form hydraulic fracturing zone (0521). Thereafter the stage(0521) is hydraulically fracturing. Similarly, hydraulic fracturing zone(0520) is created and hydraulically fractured.

According to one aspect of a preferred exemplary embodiment, RSMs may beset by WST at desired locations to enable RPEs to create multiplehydraulic fracturing zones in the wellbore casing. The hydraulicfracturing zones may be equally spaced or unevenly spaced depending onwellbore conditions or hydrocarbon formation locations.

According to another preferred exemplary embodiment, RPEs are locked inplace due to pressure differential established across RSMs. For example,RPE (0502) is locked in the seat of RSM (0512) due to a positivepressure differential established across RSM (0512) i.e., pressureupstream (hydraulic fracturing stages 0520, 0521 and stages towards heelof the wellbore casing) is greater than pressure downstream (hydraulicfracturing stages 0522, 0523 and stages towards toe of the wellborecasing).

According to a further preferred exemplary embodiment, RPEs (0501, 0502,0503) may degrade over time, flowed back by pumping, or flowed into thewellbore, after completion of all stages in the wellbore, eliminatingthe need for additional milling operations.

According to a further preferred exemplary embodiment the RPE's maychange shape or strength such that they may pass through a RSM in eitherthe production (heel end) or injection direction (toe end). For exampleRPE (0512) may degrade and change shape such that it may pass throughRSM (0511) in the production direction or RSM (0513) in the injectiondirection. The RPEs may also be degraded such that they are in betweenthe RSMs of current stage and a previous stage restricting fluidcommunication towards the injection end (toe end) but enabling fluidflow in the production direction (heel end). For example, RPE (0502) maydegrade such that it is seated against the injection end (toe end) ofRSM (0511) that may have flow channels. Flow channels in the RSM arefurther described below in FIG. 32 (3200) and FIG. 34 (3400).

According to yet another preferred exemplary embodiment, inner diametersof RSMs (0511, 0512, 0513) may be the same and large enough to allowunrestricted fluid flow during well production operations. The RSMs(0511, 0512, 0513) may further degrade in well fluids to provide an evenlarger diameter comparable to the inner diameter of the well casing(0504) allowing enhanced fluid flow during well production. Thedegradation could be accelerated by acids in the hydraulic fracturingfluids.

Preferred Exemplary Restriction Plug Elements (RPE)

It should be noted that some of the material and designs of the RPEdescribed below may not be limited and should not be construed as alimitation. This basic RPE design and materials may be augmented with avariety of ancillary embodiments, including but not limited to:

-   -   Made of multi layered materials, where at least one layer of the        material melts or deforms at temperature allowing the size or        shape to change.    -   May be a solid core with an outer layer of meltable material.    -   May or may not have another outer layer, such as a rubber        coating.    -   May be a single material, non-degradable.    -   Outer layer may or may not have holes in it, such that an inner        layer could melt and liquid may escape.    -   Passage ways through them which are filled with meltable,        degradable, or dissolving materials.    -   Use of downhole temperature and pressure, which change during        the stimulation and subsequent well warm up to change the shape        of barriers with laminated multilayered materials.    -   Use of a solid core that is degradable or erodible.    -   Use of acid soluble alloy balls.    -   Use of water dissolvable polymer frac balls.    -   Use of poly glycolic acid balls.

Preferred Exemplary Wellbore Plug Isolation Flowchart Embodiment (0600)

As generally seen in the flow chart of FIG. 6 (0600), a preferredexemplary wellbore plug isolation method may be generally described interms of the following steps:

-   -   (1) installing the wellbore casing (0601);    -   (2) deploying the WST along with the RSM to a desired wellbore        location in the wellbore casing along with a perforating gun        string assembly (GSA); the WST could be deployed by wireline,        coil tube, or tubing-conveyed perforating (TCP) (0602); the        perforating GSA may comprise plural perforating guns;    -   (3) setting the RSM at the desired wellbore location with the        WST; the WST could set RSM with a power charge or pressure        (0603); The power charge generates pressure inside the setting        tool that sets the RSM; the RSM may or may not have a conforming        seating surface (CSS); the CSS may be machined or formed by the        WST at the desired wellbore location;    -   (4) perforating hydrocarbon formation with the perforating GSA;        the perforating GSA may perforate one interval at a time        followed by pulling the GSA and perforating the next interval in        the stage; the perforation operation is continued until all the        intervals in the stage are completed;    -   (5) removing the WST and the perforating GSA from the wellbore        casing; the WST could be removed by wireline, coil tube, or TCP        (0605);    -   (6) deploying the RPE to seat in the RSM isolating fluid        communication between upstream (heel or production end) of the        RSM and downstream (toe or injection end) of the RSM and        creating a hydraulic fracturing stage; RPE may be pumped from        the surface, deployed by gravity, or set by a tool; If a CSS is        present in the RSM, the RPE may be seated in the CSS; RPE and        CSS complementary shapes enable RPE to seat into the CSS;        positive differential pressure may enable RPE to be driven and        locked into the CSS (0606);    -   (7) fracturing the hydraulic fracturing stage; by pumping        hydraulic fracturing fluid at high pressure to create pathways        in hydrocarbon formations (0607);    -   (8) checking if all hydraulic fracturing stages in the wellbore        casing have been completed, if not so, proceeding to step        (0602); prepare to deploy the WST to a different wellbore        location towards the heel end of the already fractured stage;        hydraulic fracturing stages may be determined by the length of        the casing installed in the hydrocarbon formation; if all stages        have been fractured proceed to step (0609), (0608);    -   (9) enabling fluid flow in the production (heel end) direction;        fluid flow may been enabled through flow channels designed in        the RSM while the RPEs are positioned in between the RSMs; fluid        flow may also be been enabled through flow channels designed in        the RPEs and RSMs; alternatively RPEs may also be removed from        the wellbore casing or the RPEs could be flowed back to surface,        pumped into the wellbore, or degraded in the presence of        wellbore fluids or acid (0609); and    -   (10) commencing oil and gas production from all the        hydraulically fractured stages (0610).

Preferred Embodiment Side View Cylindrical Restriction Plug System BlockDiagram (0700, 0800)

One preferred embodiment may be seen in more detail as generallyillustrated in FIG. 7 (0700) and FIG. 8 (0800), wherein a cylindricalrestrictive plug element (0702) is seated in CSS (0704) to providedownstream pressure isolation. A wellbore casing (0701) is installed ina hydrocarbon formation. A wellbore setting tool may set RSM (0703) at adesired location and seal it against the inside surface of the wellborecasing (0701). The WST may form a CSS (0704) in the RSM (0703) asdescribed by foregoing method described in FIG. 6 (0600). According toone preferred exemplary embodiment, a cylindrical shaped restrictiveplug element (RPE) (0702) may be deployed into the wellbore casing toseat in CSS (0704).

The diameter of the RPE (0702) is chosen such that it is less than theouter diameter and greater than the inner diameter of RSM (0703). TheCSS (0704) and RPE (0702) may be complementary shaped such that RPE(0702) seats against CSS (0704). For example, RPE (0702) may becylindrically shaped and CSS (0704) may be beveled shaped to enable RPE(0702) to seat in CSS (0704) when a differential pressure is applied.The RPE (0702) may pressure lock against CSS (0704) when differentialpressure is applied.

It should be noted that, if a CSS is not present in the RSM (0703) ornot formed by the WST, the cylindrical RPE (0702) may directly seatagainst the edges of the RSM (0703).

Preferred Embodiment Side View Dart Restriction Plug System BlockDiagram (0900-1020)

Yet another preferred embodiment may be seen in more detail as generallyillustrated in FIG. 9 (0900), FIG. 10 (1000), FIG. 10a (1010), and FIG.10b (1020) wherein a dart shaped restrictive plug element (0902) isseated in CSS (0904) to provide pressure isolation. According to asimilar process described above in FIG. 7, RPE (0902) is used to isolateand create fracture zones to enable perforation and hydraulic fracturingoperations in the fracture zones. As shown in the perspective views ofthe dart RPE in FIG. 10a (1010) and FIG. 10b (1020), the dart RPE iscomplementarily shaped to be seated in the RSM. The dart RPE (0902) isdesigned such that the fingers of the RPE (0902) are compressed duringproduction enabling fluid flow in the production direction.

Preferred Embodiment Side Cross Section View of a Restriction SleeveMember System Block Diagram (1100, 1200)

One preferred embodiment may be seen in more detail as generallyillustrated in FIG. 11 (1100) and FIG. 12 (1200), wherein a restrictivesleeve member RSM (1104) is sealed against the inner surface of awellbore casing (1101) with a plurality of gripping/sealing elements(1103). Gripping elements may be elastomers, carbide buttons, or wickerforms. After a wellbore casing (1101) is installed, a wellbore settingtool may be deployed along with RSM (1104) to a desired wellborelocation. The WST may then compress the RSM (1104) to form plural innerprofiles (1105) on the inside surface of the RSM (1104) at the desiredlocation. In one preferred exemplary embodiment, the inner profiles(1105) may be formed prior to deploying to the desired wellborelocation. The compressive stress component in the inner profiles (1105)may aid in sealing the RSM (1104) to the inner surface of a wellborecasing (1101). A plurality of gripping/sealing elements (1103) may beused to further strengthen the seal (1106) to prevent substantial axialor longitudinal movement of RSM (1104). The gripping elements (1103) maybe an elastomer, carbide buttons, or wicker forms that can tightly gripagainst the inner surface of the wellbore casing (1101). The seal (1106)may be formed by plural inner profiles (1105), plural gripping elements(1103), or a combination of inner profiles (1105) and gripping elements(1103). Subsequently, the WST may form a CSS and seat a RPE (1102) tocreate downstream isolation (toe end) as described by the foregoingmethod in FIG. 6 (0600).

Preferred Embodiment Side Cross Section View of Inner and Outer Profilesof a Restriction Sleeve Member System Block Diagram (1300-1700)

Yet another preferred embodiment may be seen in more detail as generallyillustrated in FIG. 13 (1300), wherein a restrictive sleeve member RSM(1304) is sealed against the inner surface of a wellbore casing (1301).After a wellbore casing (1301) is installed, a wellbore setting tool maybe deployed along with RSM (1304) to a desired wellbore location. TheWST may then compress the RSM (1304) to form plural inner profiles(1305) on the inside surface of the RSM (1304) and plural outer profiles(1303) on the outside surface of the RSM (1304) at the desired location.In one preferred exemplary embodiment, the inner profiles (1305) andouter profiles (1303) may be formed prior to deploying to the desiredwellbore location. The compressive stress component in the innerprofiles (1305) and outer profiles (1303) may aid in sealing the RSM(1304) to the inner surface of a wellbore casing (1301). The outerprofiles (1303) may directly contact the inner surface of the wellborecasing at plural points of the protruded profiles to provide a seal(1306) and prevent axial or longitudinal movement of the RSM (1304).FIG. 14 (1400) illustrates a detailed cross section view of a WSTforming a seal against the inner surface of the wellbore casing.

Similarly, FIG. 15 (1500) illustrates a wireline setting tool creatinginner and outer profiles in restriction sleeve members for sealingagainst the inner surface of the wellbore casing. FIG. 16 illustrates adetailed cross section view of a WST (1603) that forms an inner profile(1604) in a RSM (1602) to form a seal (1605) against the inner surfaceof wellbore casing (1601). Likewise, FIG. 17 (1700) illustrates adetailed cross section view of a WST (1703) that forms an inner profile(1704) and an outer profile (1706) in a RSM (1702) to form a seal (1705)against the inner surface of wellbore casing (1701). According to apreferred exemplary embodiment, inner and outer profiles in a RSM formsa seal against an inner surface of the wellbore casing preventingsubstantial axial and longitudinal movement of the RSM duringperforation and hydraulic fracturing process.

Preferred Embodiment Wellbore Setting Tool (WST) System Block Diagram(1800-2200)

FIG. 18 (1800) and FIG. 19 (1900) show a front cross section view of aWST. According to a preferred exemplary embodiment, a wellbore settingtool (WST) may be seen in more detail as generally illustrated in FIG.20 (2000). A WST-RSM sleeve adapter (2001) holds the RSM (2008) in placeuntil it reaches the desired location downhole. After the RSM (2008) isat the desired location the WST-RSM sleeve adapter (2001) facilitates areactionary force to engage the RSM (2008). When the WST (2002) isactuated, a RSM swaging member and plug seat (2005) provides the axialforce to swage an expanding sleeve (2004) outward. A RSM-ICD expandingsleeve (2004) hoops outward to create a sealing surface between the RSM(2008) and inner casing diameter (ICD) (2009). After the WST (2002)actuation is complete, it may hold the RSM (2008) to the ICD (2009) bymeans of sealing force and potential use of other traction addingdevices such as carbide buttons or wicker forms. The WST-RSM piston(2006) transmits the actuation force from the WST (2002) to the RSM(2008) by means of a shear set, which may be in the form of a machinedring or shear pins. The connecting rod (2003) holds the entire assemblytogether during the setting process. During activation, the connectingrod (2003) may transmit the setting force from the WST (2002) to the WSTpiston (2006). FIG. 21 (2100) and FIG. 22 (2200) show perspective viewsof the WST (2002) in more detail.

Preferred Embodiment Wellbore Plug Isolation System Block Diagram(2300-3100)

As generally seen in the aforementioned flow chart of FIG. 6 (0600), thesteps implemented for wellbore plug isolation are illustrated in FIG. 23(2300)-FIG. 31 (3100).

As described above in steps (0601), (0602), and (0603) FIG. 23 (2300)shows a wellbore setting tool (WST) (2301) setting a restriction sleevemember (2303) on the inside surface of a wellbore casing (2302). The WST(2301) may create a conforming seating surface (CSS) in the RSM (2303)or the CSS may be pre-machined. A wireline (2304) or TCP may be used topump WST (2301) to a desired location in the wellbore casing (2302).FIG. 24 (2400) shows a detailed view of setting the RSM (2303) at adesired location.

FIG. 25 (2500) illustrates the stage perforated with perforating gunsafter setting the RSM (2303) and removing WST (2301) as aforementionedin steps (0604) and (0605).

FIG. 26 (2600) illustrates a restriction plug element (RPE) (2601)deployed into the wellbore casing as described in step (0606). The RPE(2601) may seat in the conforming seating surface in RSM (2303) ordirectly in the RSM if the CSS is not present. After the RPE (2601) isseated, the stage is isolated from toe end pressure communication. Theisolated stage is hydraulically fractured as described in step (0607).FIG. 27 (2700) shows details of RPE (2601) deployed into the wellborecasing. FIG. 28 (2800) shows details of RPE (2601) seated in RSM (2303).

FIG. 29 (2900) illustrates a WST (2301) setting another RSM (2903) atanother desired location towards the heel of the RSM (2303). Another RPE(2901) is deployed to seat in the RSM (2903). The RPE (2901) isolatesanother stage toeward of the aforementioned isolated stage. The isolatedstage is fractured with hydraulic fracturing fluids. FIG. 30 (3000)shows a detailed cross section view of WST (2301) setting RSM (2903) ata desired location. FIG. 31 (3100) shows a detailed cross section viewof an RPE (2901) seated in RSM (2903). When all the stages are completeas described in (0608) the RPEs may remain in between the RSMs or flowedback or pumped into the wellbore (0609). According to a preferredexemplary embodiment, the RPE's and RSM's are degradable which enableslarger inner diameter to efficiently pump oil and gas withoutrestrictions and obstructions.

Preferred Embodiment Restriction Sleeve Member (RSM) With Flow ChannelsBlock Diagram (3200-3400)

A further preferred embodiment may be seen in more detail as generallyillustrated in FIG. 32 (3200), FIG. 33 (3300) and FIG. 34 (3400),wherein a restrictive sleeve member RSM (3306) comprising flow channels(3301) is set inside a wellbore casing (3305). A conforming seatingsurface (CSS) (3303) may be formed in the RSM (3306). The flow channels(3301) are designed in RSM (3306) to enable fluid flow during oil andgas production. The flow channels provide a fluid path in the productiondirection when restriction plug elements (RPE) degrade but are notremoved after all stages are hydraulically fractured as aforementionedin FIG. (0600) step (0609). The channels (3301) are designed such thatthere is unrestricted fluid flow in the production direction (heelward)while the RPEs block fluid communication in the injection direction(toeward). Leaving the RPEs in place provides a distinct advantage overthe prior art where a milling operation is required to mill out fracplugs that are positioned to isolate stages.

According to yet another preferred embodiment, the RSMs may be designedwith fingers on either end to facilitate milling operation, if needed.Toe end fingers (3302) and heel end fingers (3304) may be designed onthe toe end and heel end the RSM (3306) respectively. In the context ofa milling operation, the toe end fingers may be pushed towards the heelend fingers of the next RSM (toeward) such that the fingers areintertwined and interlocked. Subsequently, all the RSMs may beinterlocked with each other finally eventually mill out in one operationas compared to the current method of milling each RSM separately.

Preferred Embodiment Wellbore Setting Tool (WST) System Double Set BlockDiagram (3500-3700)

As generally illustrated in FIG. 35 (3500), FIG. 36 (3600) and FIG. 37(3700) a wellbore setting tool sets or seals on both sides of arestriction sleeve member (RSM) (3601) on the inner casing surface (ICS)(3604) of a wellbore casing. In this context the WST swags the RSM onboth sides (double set) and sets it to the inside surface of thewellbore casing. On one end of the RSM (3601), a RSM-ICD expandingsleeve in the WST may hoop outward to create a sealing surface betweenthe RSM (3601) and ICS (3604). On the other side of the RSM (3601), whenWST actuation is complete, the WST may hold the RSM (3601) to the ICS(3604) by means of sealing force and potential use of other tractionadding gripping devices (3603) such as elastomers, carbide buttons orwicker forms.

According to a preferred exemplary embodiment, a double set option isprovided with a WST to seal one end of the RSM directly to the innersurface of the wellbore casing while the other end is sealed with agripping element to prevent substantial axial and longitudinal movement.

Preferred Embodiment Wellbore Setting Tool (WST) System Multiple SetBlock Diagram (3800-4100)

As generally illustrated in FIG. 38 (3800), FIG. 39 (3900), FIG. 40(4000), and FIG. 41 (4100) a wellbore setting tool sets or seals RSM atmultiple locations. FIG. 38 (3800) shows a WST (3810) that may set orseal RSM at single location (single set), a WST (3820) that may set orseal RSM at double locations (double set), or a WST (3830) that may setor seal RSM 3 locations (triple set). A more detail illustration of WST(3830) may be seen in FIG. 40 (4000). The WST (3830) sets RSM (4004) at3 locations (4001), (4002), and (4003). According to a preferredexemplary embodiment, WST sets or seals RSM at multiple locations toprevent substantial axial or longitudinal movement of the RSM. It shouldbe noted that single, double and triple sets have been shown forillustrative purposes only and should not be construed as a limitation.The WST could set or seal RSM at multiple locations and is not limitedto single, double, or triple set as aforementioned. An isometric view ofthe triple set can be seen in FIG. 41 (4100).

Preferred Embodiment Restriction Sleeve Member Polished Bore Receptacle(PBR)

According to a preferred exemplary embodiment, the restricted sleevemember could still be configured with or without a CSS. The inner sleevesurface (ISS) of the RSM may be made of a polished bore receptacle(PBR). Instead of an independently pumped down RPE, however, a sealingdevice could be deployed on a wireline or as part of a tubular string.The sealing device could then seal with sealing elements within therestricted diameter of the internal sleeve surface (ISS), but not in theICS surface. PBR surface within the ISS provides a distinct advantage ofselectively sealing RSM at desired wellbore locations to performtreatment or re-treatment operations between the sealed locations, wellproduction test, or test for casing integrity.

Preferred Embodiment Restriction Plug Element

Restriction plug element such as balls with large aspect ratioapproaching 1 and seated in a large inner diameter restriction sleevemember do not degrade in wellbore fluids. The plug elements change shapefrom a circular to flying saucer shape because water is restricted onthe edge and a sand pack that holds the ball on the seat prevents theplug element from interacting with the water and wellbore fluids.Therefore there is a need to add a mechanism to provide more surfacearea in the restriction plug element to contact with the restrictionplug element after seating in a restriction sleeve member. According toa preferred exemplary embodiment, a partially hollow passage, (hereinalso referenced as a partial Flow channel) in the restriction plugelement enables the plug element to seat in a restriction sleeve memberduring treatment and subsequently degrade to form a complete hollowpassage so that there is a higher probability for water and wellboreliquids to back flow and degrade the restriction plug element. Thecomplete flow channel dissolves or degrades not only the outside butalso the inside of the wall of the restriction plug element. Initiallythe flow is restricted by the closed end in the partial hollow passageand over time the flow channel opens up by degradation and allows fluidto pass through in either direction. During back flow in the well newfluid is circulated into the well and the restriction plug elementcontinues to degrade. It should be noted that the terms “flow channel”and “hollow passage” may hereinafter be interchangeably used referencinga hollow cavity within a restriction plug element.

According to a preferred exemplary embodiment, a restriction plugelement for use in a wellbore casing may comprise a degradable materialand be configured with a partial hollow passage extending from at leastone interior end. The interior end configured to block fluidcommunication from upstream to downstream during fluid treatment and thepartial hollow passage configured to degrade and form a complete hollowpassage to enable said fluid communication subsequent to the fluidtreatment.

According to another preferred exemplary embodiment the interior end isfurther configured with an terminus; the terminus configured to orientsuch that the restriction plug element seats in a restriction sleevemember and restricts substantial fluid bypass during a fluid treatment.The terminus may include any shape such as a nose, a conical shape, or atail (arrow terminus). The orientation feature may enable changing thecenter of rotation so that there is a preferred rotation axis while therestriction plug element is being pumped down. For instance, a ball witha single hollow passage will preferentially rotate around the axis ofthat hollow passage, and therefore orient itself. It should be notedthat ball may orient and may not orient but produce the same effectseating in a restriction sleeve member.

The hollow passage may be machined by drilling a cavity into a body of adegradable material restriction plug element (“ball”), such that thereis a thinner web section that would degrade more quickly, creating aflow channel through the ball which further enhances degradation, andmore surface area with which to speed the degradation rate of thecomposite ball. The pattern and the size of the holes will have designconsiderations so that they create a sufficient flow path or increase insurface area, while not compromising the seating of the ball. The holescould be drilled from one side leaving a web, or drilled from theoutside to the center, leaving a small core which would need to degrade.The holes may be subsequently capped with degradable or non-degradablematerial. Small amounts of eutectic metal, or non-degradable metal,composite, or injection molded structures with flow channels could beused to support the inner structure of the ball. The altered center ofmass could determine the likelihood that the ball would seat on anyparticular orientation. This could be manipulated advantageously inorder to position the ball on the seat as desired. According to apreferred exemplary embodiment the ball seals when seated on restrictionsleeve member during a fracture treatment while the holes in the partialhollow passage are not blocked to prevent the seating. An arrow tail orterminus on the interior end of the ball may force the ball to land in asealing position (holes not on the seat). For example the ball mayorient such that the hollow passage (flow channel) is substantiallyparallel to the wellbore casing in a horizontal well.

As generally illustrated in FIG. 42, a cross section view (4200) and aperspective view (4210) of a restriction plug element comprises adegradable material (4202), a hollow passage (4201) having an interiorend (4203) extending to a surface end (4204). The interior end (4203)and the surface end (4204) may form the two ends of the hollow passage(4201). Illustrated in the perspective view (4210) is an arrow shapedterminus (4205) in the interior end (4203). The thin section (4206) mayextend from the interior end into the solid body of the material (4202).The restriction plug element (4200) may be dropped into a wellborecasing for isolating stages. An arrow tail (4205) or terminus on theinterior end (4203) of the element (4200) may force the element to landin a sealing position (holes not on the seat). The material of the body(4202) of the restriction plug element may comprise a degradablematerial. A partial hollow passage (4201) may extend from an interiorend (4203) in the core of the plug element (4200). The interior end(4203) in the hollow passage (4201) and the thin section (4205) mayblock fluid communication from upstream (heel end) to downstream (toeend) during fluid treatment. The partial hollow passage (4201) enableswater and other wellbore fluids to come in contact with the partialhollow passage and enable degradation such that a complete hollowpassage is formed. The complete hollow passage may enable fluidcommunication subsequent to the fluid treatment. The hollow passage(4201) may be machined by drilling a cavity into a body (4202) of adegradable material restriction plug element (“ball”) (4200), such thatthere is a thinner web section (4206) that would degrade more quickly,creating a complete flow channel (4201) through the ball (4200) whichfurther enhances degradation, and more surface area with which to speedthe degradation rate of the composite ball (4200). During back flow inthe well new fluid is circulated into the well and the restriction plugelement continues to degrade.

According to a preferred exemplary embodiment the complete hollowpassage enables the restriction plug element to deform such that therestriction plug element passes through a restriction sleeve member inthe wellbore casing. According to another preferred exemplary embodimenta shape of the restriction plug element is selected from a groupcomprised of: circular, cylinder, sphere, oval or elongated. Accordingto yet another preferred exemplary embodiment a shape of cross sectionof said hollow passage is selected from a group comprised of: circle,square, oval or elongated.

According to a preferred exemplary embodiment the partial hollow passageis capped at an open end with a degradable material. The open end andthe interior end forming two ends of said hollow passage. For example,interior end (4203) and open end or surface end (4204) may form two endsof hollow passage (4201). The open end (4204) may be capped with adegradable material that degrades in the presence of wellbore fluidsexpected in the wellbore casing. According to another preferredexemplary embodiment the partial hollow passage extends to a surface ofthe restriction plug element.

According to another preferred exemplary embodiment the partial hollowpassage may extend from one interior end to another interior end. Forexample interior end (4201) may not extend all the way to the surfacebut terminate interior to the core leaving a thin web section similar tosection (4206). Therefore, the two ends of the hollow passage may beinterior to the core. The thin sections of on either ends may degradeand form a complete open flow channel or passage. According to yetanother preferred exemplary embodiment the partial hollow passage passesthrough a center of the restriction plug element. According to a furtherpreferred exemplary embodiment the partial hollow passage does not passthrough a center of the restriction plug element. For example passage(4201) may be slightly offset from the center and achieve a similarresult as a passage that passes through the center of the plug element.

FIG. 43 generally illustrates a restriction plug element (4300)comprising a plurality of partial hollow passages (4301, 4302, 4303,4304, 4305, 4306) that extend from respective interior end. According toa preferred exemplary embodiment the flow channels may be aligned toeach other. According to another preferred exemplary embodiment at leastone of the partial hollow passage is aligned to another partial hollowpassage.

For example, flow channel (4301) and flow channel (4304) are aligned toeach other and an axis through the channel may pass through the centerof the restriction plug element (4300). Similarly flow channel (4302)and flow channel (4305), flow channel (4303) and flow channel (4306) maybe aligned to each other. The partial flow channels may further degradeand form complete flow channels extending diametrically or cordiallyfrom a surface end/hole to another surface hole/end. The increasedsurface area in the completed flow channels may further enhance thedegradation of the restriction plug element (4300). A perspective view(4310) of the restriction plug element is generally illustrated in FIG.43.

According to a preferred exemplary embodiment at least one of thepartial hollow passage intersects with at least one other partial hollowpassage. For example, partial flow channel (4302) may be drilled with anangle such that it intersects channel (4301) or channel (4303) dependingon the angle of drilling.

According to a preferred exemplary embodiment at least one of thepartial hollow passages does not intersect with any other partial hollowpassage. For example, all the partial hollow passages in FIG. 43 do notintersect with each other before degradation.

According to another preferred exemplary embodiment at least one of thepartial hollow passages comprises a plurality of interior ends. Theplurality of interior ends may be spread out or fanned out. For example,one partial hollow passage may form plural passage ways with a pluralityof interior ends that degrade and complete the channels. An end view(4310) of restriction plug element (4300) is generally illustrated inFIG. 43. A perspective view (4320) along cross section (4330) isgenerally illustrated in FIG. 43.

FIG. 44 generally illustrates perspective view of a partial flow channeltransforming to complete flow channel in a restriction plug element(4400). Before and during a fracture treatment, partial flow channels(4401, 4402, 4403, 4404) block fluid communication from upstream todownstream and in reverse direction. Subsequent to a fracture treatment,the interior ends of each of the channels (4401, 4402, 4403, 4404) maydegrade towards the center (4405) of the core and transform into fullycomplete flow channels and enabling fluid communication in eitherdirection. The fully complete channels, illustrated in FIG. 44 (4410),provide for more surface area for wellbore fluids to come into contactwith the restriction plug element and subsequently degrade the plugelement (4400) in the presence of the wellbore fluids.

According to another preferred exemplary embodiment, the restrictionplug element may comprise at least one partial hollow passage extendingto a surface of the restriction plug element on both ends of said flowchannel creating a complete passage. For example, as illustrated in anend view of FIG. 45 (4500), flow channel (4501) extends from a surfacethrough the center to the other surface end of the restriction plugelement. The complete hollow passage may provide some of the samebenefits as a partial passage if the ball is configured to seat in sucha way as the passage does not communicate across a restriction sleevemember. If the complete passage (4501) does communicate across therestriction sleeve, but is small enough, the same effect of increasedsurface area and dissolve rate may be achieved. Other flow channels(4502, 4503, 4504, 4505) are partial flow channels with interior endsthat may degrade in wellbore fluids. The opening of the channel (4501)may be capped with a degradable material during treatment and blockfluid communication. A cross section view (4510), perspective view(4520) of section (4506) and a perspective view (4530) of section (4507)is generally illustrated in FIG. 45.

Preferred Exemplary Flowchart Embodiment of a Restriction Plug ElementDegradation Method (4600)

As generally seen in the flow chart of FIG. 46 (4600), a preferredexemplary flowchart embodiment of a restriction plug element degradationmethod in conjunction with a restriction plug element (RPE) for use in awellbore casing; said restriction plug element comprising a degradablematerial; said restriction plug element configured with at least onepartial hollow passage that extends from an interior end may begenerally described in terms of the following steps:

-   -   (1) deploying the restriction plug element into the wellbore        casing and blocking fluid communication (4601);        -   The restriction plug element may be pumped down or dropped            down to seat in a restriction sleeve member at a desired            location.    -   (2) orienting the restriction plug element with the interior end        to seat in a restriction sleeve member and isolating a stage        (4602);        -   An arrow tail or terminus on the interior end of the ball            may force the ball to land in a sealing position (holes not            on the seat). For example the ball may orient such that the            hollow passage (flow channel) is substantially parallel to            the wellbore casing in a horizontal well. According to a            preferred exemplary embodiment, the orienting step (4602)            further seals the restriction plug element to restrict            substantial fluid bypass in the treating step (4603).            According to another preferred exemplary embodiment the            orienting step (4602) orients the restriction plug element            such that the hollow passage is unblocked by the restriction            sleeve member. The terminus may include any shape such as a            nose, a conical shape, or a tail (arrow terminus). The            orientation feature may enable changing the center of            rotation so that there is a preferred rotation axis while            the restriction plug element is being pumped down. For            instance, a ball with a single hollow passage will            preferentially rotate around the axis of that hollow            passage, and therefore orient itself. It should be noted            that ball may orient and may not orient but produce the same            effect seating in a restriction sleeve member. Therefore,            orienting step (4602) may be skipped during the degradation            method. A complete passage or partial passage may be            designed such that orienting is important, where it will            always orient, or where orienting is unimportant. The            passage may be partial or complete. The complete hollow            passage may provide some of the same benefits as a partial            passage if the ball is configured to seat in such a way as            the passage does not communicate across a restriction sleeve            member. If the complete passage does communicate across the            restriction sleeve, but is small enough, the same effect of            increased surface area and dissolve rate may be achieved.    -   (3) treating the isolated stage with fracturing fluids (4603);        -   The restriction plug elements seats and seals in a            restriction sleeve member during the treatment stage.    -   (4) degrading from the interior end in the partial hollow        passage through contact with wellbore fluids (4604);        -   The interior end starts degrading a thin section and            allowing contact of well fluids with the restriction plug            element. According to another preferred exemplary embodiment            the degrading step (4604) occurs immediately after the            treating step (4603).    -   (5) creating a complete hollow passage from the partial hollow        passage (4605); and The partial hollow passage or flow channel        may be transformed into a complete flow channel when the thin        section completely degrades. According to another preferred        exemplary embodiment the creating step (4605) accelerates rate        of degradation of the restriction plug element.    -   (6) unblocking the fluid communication (4606).

According to a further preferred exemplary embodiment the step ofdegrading the restriction plug element to deform.

According to a most preferred exemplary embodiment a ratio of diameterof the restriction plug element to an inner diameter of the restrictionsleeve member ranges from 0.5 to 0.99.

Mass Vs Time and Diameter Vs Time of a Solid Ball and a PreferredExemplary Hollow Passage Restriction Plug Element (4700-4800)

FIG. 47 (4700) generally illustrates experimental data of a mass vs.time chart for a solid ball (4702) and a preferred exemplary partialhollow passage restriction plug element (4701). The dissolve rate of theexemplary restriction plug is substantially higher than a solid ball.The exemplary restriction plug may include drilled hollow passages andorienting features as aforementioned in FIGS. 42, 43, 44, 45. FIG. 48(4800) generally illustrates experimental data of a diameter vs. timechart for a solid ball (4802) and a preferred exemplary partial hollowpassage restriction plug element (4801). It should be noted that thedata illustrated in FIG. 47 (4700) and FIG. 48 (4800) are taken from thesame experiment for the same solid ball and a ball with a drilled hole.The exemplary hollow passage restriction plug element also referredherein as ball with the drilled hole or drilled ball, reduced diameterat the same rate as the solid ball (i.e. would stay on seat for the sametime) but the reduction in mass was improved such that the ball with thedrilled hole fully dissolved much more quickly. This is due to theincrease in surface area, but more importantly, the fact that theexemplary hollow passage restriction plug element dissolves from theinside and the outside at the same time, thus improving the time toremoval of the ball while plugging the seat for the same amount of time.The charts (4700, 4800) demonstrate experimental tests where thediameter of the exemplary ball with drilled hole reduced at the samerate as the solid ball, but the time to total degradation issignificantly reduced by the addition of the hollow passage. The shapeof the internal hollow can be manipulated in order to change thecharacteristic of the dissolve rate and the exposure of the surface areaof the drilled ball to wellbore fluids. For example, at a time stamp of60 hours the diameters of the solid ball and the drilled ball issubstantially the same at approximately 3.75 in. However at the sametime stamp of 60 hours, the mass of the solid ball is approximately 410grams and the mass of the drilled ball is 210 grams. The preferredexemplary chart clearly demonstrates the reduction in mass was improvedsuch that the ball with the drilled hole fully dissolved much morequickly. Furthermore, this is due to the increase in surface area, butmore importantly, the fact that the exemplary hollow passage restrictionplug element dissolves from the inside and the outside at the same time,thus improving the time to removal of the ball while plugging the seatfor the same amount of time.

System Summary

The present invention system anticipates a wide variety of variations inthe basic theme of extracting gas utilizing wellbore casings, but can begeneralized as a restriction plug element for use in a wellbore casing,the restriction plug element comprising a degradable material; therestriction plug element configured with a partial hollow passageextending from at least one interior end; the interior end configured toblock fluid communication from upstream to downstream during fluidtreatment; and the partial hollow passage configured to degrade and forma complete hollow passage to enable the fluid communication subsequentto the fluid treatment.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Method Summary

The present invention method anticipates a wide variety of variations inthe basic theme of implementation, but can be generalized as arestriction plug element degradation method, the method operating inconjunction with a restriction plug element (RPE) for use in a wellborecasing, the restriction plug element comprising a degradable material;the restriction plug element configured with at least one partial hollowpassage that extends from an interior end;

-   -   wherein the method comprises the steps of:    -   (1) deploying the restriction plug element into the wellbore        casing and blocking fluid communication;    -   (2) orienting the restriction plug element with the interior end        to seat in a restriction sleeve member and isolating a stage;    -   (3) treating the isolated stage with fracturing fluids;    -   (4) degrading from the interior end in the partial hollow        passage through contact with wellbore fluids;    -   (5) creating a complete hollow passage from the partial hollow        passage; and    -   (6) unblocking the fluid communication.

This general method summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

System/Method Variations

The present invention anticipates a wide variety of variations in thebasic theme of oil and gas extraction. The examples presented previouslydo not represent the entire scope of possible usages. They are meant tocite a few of the almost limitless possibilities.

This basic system and method may be augmented with a variety ofancillary embodiments, including but not limited to:

-   -   An embodiment wherein the interior end is further configured        with an arrow terminus; the arrow terminus configured to orient        such that the restriction plug element seats in a restriction        sleeve member and restricts substantial fluid bypass during the        fluid treatment.    -   An embodiment wherein the partial hollow passage substantially        increases a surface area of contact of the restriction plug        element with fluids expected in the wellbore casing.    -   An embodiment wherein the partial hollow passage is capped at an        open end with a degradable material; the open end and the        interior end forming two ends of the hollow passage.    -   An embodiment wherein the partial hollow passage extends from        the interior end to another interior end.    -   An embodiment wherein the partial hollow passage extends to a        surface of the restriction plug element.    -   An embodiment further comprises at least one partial hollow        passage extending to a surface of the restriction plug element        on both ends of the flow channel.    -   An embodiment wherein the partial hollow passage passes through        a center of the restriction plug element.    -   An embodiment wherein at least one of the partial hollow        passages intersects with at least one other partial hollow        passage.    -   An embodiment wherein at least one of the partial hollow        passages does not intersect with any other partial hollow        passage.    -   An embodiment wherein at least one of the partial hollow        passages comprises a plurality of interior ends; the plurality        of interior ends are configured to be spread out.    -   An embodiment whereby the complete hollow passage enables the        restriction plug element to deform such that the restriction        plug element passes through a restriction sleeve member in the        wellbore casing.    -   An embodiment wherein at least one of the partial hollow        passages is aligned to another partial hollow passage.    -   An embodiment wherein a shape of the restriction plug element is        selected from a group comprised of: circular, cylinder, sphere,        oval or elongated.    -   An embodiment wherein a shape of cross section of the hollow        passage is selected from a group comprised of: circle, square,        oval or elongated.

One skilled in the art will recognize that other embodiments arepossible based on combinations of elements taught within the aboveinvention description.

CONCLUSION

A restriction plug element and method for positioning plugs to isolatefracture zones in a horizontal, vertical, or deviated wellbore has beendisclosed. The restriction plug element includes a partial hollowpassage with an interior end. The partial passage enables the plugelement to seat in a restriction sleeve member during treatment andsubsequently degrade to form a complete hollow passage. The completeflow channel dissolves or degrades not only the outside but also theinside of the wall of the restriction plug element. Initially the flowis restricted by the closed end in the partial hollow passage and overtime the flow channel opens up by degradation and allows fluid to passthrough in either direction. During back flow in the well, new fluid iscirculated into the well and the restriction plug element continues todegrade.

Although a preferred embodiment of the present invention has beenillustrated in the accompanying drawings and described in the foregoingDescription, it will be understood that the invention is not limited tothe embodiments disclosed, but is capable of numerous rearrangements,modifications, and substitutions without departing from the spirit ofthe invention as set forth and defined by the following claims.

What is claimed is:
 1. A restriction plug element for use in a wellborecasing, said restriction plug element comprising a degradable material;said restriction plug element configured with a partial hollow passageextending from at least one interior end; said interior end configuredto block fluid communication from upstream to downstream during fluidtreatment; and said partial hollow passage configured to degrade andform a complete hollow passage to enable said fluid communicationsubsequent to said fluid treatment.
 2. The restriction plug element ofclaim 1 wherein said interior end is further configured with a terminus;said terminus configured to orient such that said restriction plugelement seats in a restriction sleeve member and restricts substantialfluid bypass during said fluid treatment.
 3. The restriction plugelement of claim 1 wherein said partial hollow passage substantiallyincreases a surface area of contact of said restriction plug elementwith fluids expected in said wellbore casing.
 4. The restriction plugelement of claim 1 wherein said partial hollow passage is capped at anopen end with a degradable material; said open end and said interior endforming two ends of said partial hollow passage.
 5. The restriction plugelement of claim 1 wherein said partial hollow passage extends from saidinterior end to another interior end.
 6. The restriction plug element ofclaim 1 wherein said partial hollow passage extends to a surface of saidrestriction plug element.
 7. The restriction plug element of claim 1further comprises at least one of said partial hollow passages extendingto said surface of said restriction plug element on both ends of a flowchannel.
 8. The restriction plug element of claim 1 wherein said partialhollow passage passes through a center of said restriction plug element.9. The restriction plug element of claim 1 wherein at least one saidpartial hollow passage intersects with at least one other partial hollowpassage.
 10. The restriction plug element of claim 1 wherein at leastone said partial hollow passage does not intersect with any other saidpartial hollow passage.
 11. The restriction plug element of claim 1wherein at least one said partial hollow passage comprises a pluralityof interior ends; said plurality of interior ends are configured to bespread out.
 12. The restriction plug element of claim 1 whereby saidcomplete hollow passage enables said restriction plug element to deformsuch that said restriction plug element passes through a restrictionsleeve member in said wellbore casing.
 13. The restriction plug elementof claim 1 wherein at least one of said partial hollow passage isaligned to another partial hollow passage.
 14. The restriction plugelement of claim 1 wherein a shape of said restriction plug element isselected from a group comprising: circular, cylinder, sphere, oval orelongated.
 15. The restriction plug element of claim 1 wherein a shapeof cross section of said hollow passage is selected from a groupcomprising: circle, square, oval or elongated.
 16. A restriction plugelement degradation method, said method operating in conjunction with arestriction plug element (RPE) for use in a wellbore casing, saidrestriction plug element comprising a degradable material; saidrestriction plug element configured with at least one partial hollowpassage that extends from an interior end; wherein said method comprisesthe steps of: (1) deploying said restriction plug element into saidwellbore casing and blocking fluid communication; (2) orienting saidrestriction plug element with said interior end to seat in a restrictionsleeve member and isolating a stage; (3) treating said isolating stagewith fracturing fluids; (4) degrading from said interior end in saidpartial hollow passage through contact with wellbore fluids; (5)creating a complete hollow passage from said partial hollow passage; and(6) unblocking said fluid communication.
 17. The restriction plugelement degradation method of claim 16 wherein said orienting step (2)further seals said restriction plug element to restrict substantialfluid bypass in said treating step (3).
 18. The restriction plug elementdegradation method of claim 16 wherein said orienting step (2) orientssaid restriction plug element such that said hollow passage is unblockedby said restriction sleeve member.
 19. The restriction plug elementdegradation method of claim 16 wherein said orienting step (2) seatssaid restriction plug element but not orientated.
 20. The restrictionplug element degradation method of claim 16 wherein said degrading step(4) occurs immediately after said treating step (3).
 21. The restrictionplug element degradation method of claim 16 wherein said creating step(5) accelerates rate of degradation of said restriction plug element.22. The restriction plug element degradation method of claim 16 furthercomprises the step of degrading said restriction plug element to deform.23. The restriction plug element degradation method of claim 16 whereina ratio of diameter of said restriction plug element to an innerdiameter of said restriction sleeve member ranges from 0.5 to 0.99.